Devices for injection of gaseous streams into a bed of fluidized solids

ABSTRACT

Injection nozzles for use in a gas distribution device are disclosed. In one aspect, the injection nozzle may include: a tube having a fluid inlet and a fluid outlet; wherein the inlet comprises a plurality of flow restriction orifices. In another aspect, embodiments disclosed herein relate to an injection nozzle for use in a gas distribution device, the injection nozzle including: a tube having a fluid inlet and a fluid outlet; wherein the fluid inlet comprises an annular orifice surrounding a flow restriction device. Injection nozzles according to embodiments disclosed herein may be disposed in a gas distribution manifold used in a vessel, for example, for conducting polymerization reactions, spent catalyst regeneration, and coal gasification, among others.

CROSS-REFERENCE TO RELATED APPLICATION

This application, pursuant to 35 U.S.C. §120, claims benefit to U.S.patent application Ser. No. 12/418,943 filed Apr. 6, 2009, now U.S. Pat.No. ______. That application is incorporated by reference in itsentirety.

BACKGROUND OF DISCLOSURE

1. Field of the Disclosure

Embodiments disclosed herein relate generally to an apparatus for theinjection of a gaseous stream into a bed of fluidized solids. Morespecifically, embodiments disclosed herein relate to an injectionnozzle.

2. Background

In the refining and chemical process industries, as well as in otherprocessing industries, it is often necessary to inject a gaseous streaminto a bed of finely divided solids, uniformly spreading the gas overthe cross section of the bed and. The injection of the gas is designedto promote uniform and intimate contact of the gaseous medium with thebed of solids so as to achieve a purpose, such as a chemical reactionbetween the gas and solids and/or a mass transfer operation between thegas and solids.

Apparatus for injecting the gas into a fluidized bed typically consistsof a flat grid plate with holes, a pipe grid system, or a series ofconcentric rings. These distributors are designed to physically cover asmuch of the bed cross section as possible so as to promote the evendistribution of the gas across the entire bed. Gas is introduced intothe space beneath the flat plate distributor or into the main header ofa pipe grid and/or the ring distributor from a central source. Fromthere the gas flows throughout the pipe grid or ring system and thendischarges into the bed through a multiplicity of nozzles thatdistribute the gas uniformly into the bed. Plate grid distributors aretypically not completely flat but are dished slightly up or down so asto better withstand the pressure exerted by the gas and/or the weight ofthe bed of solids above. Plate grid distributors may or may not containnozzles, but typically only use a pattern of holes laid out in the plateto allow gas to flow through into the bed. Other embodiments of gasdistributors for fluid beds of solids include dome type distributors andso-called “mushroom” distributors.

In order to achieve uniform distribution of the gas medium, theinjection nozzles are typically designed with a cross sectional areathat will cause a pressure drop to occur as the gas flows through theinjection nozzles from the distribution header into the bed of solids.The maintenance of a positive pressure drop across the injection nozzlesinsures that the gas flows evenly to all of the injection nozzles inspite of differences that can occur in the pressure in the bed at thepoint of discharge. Once the gas flows upward through the bed of solids,the bed becomes “fluidized” and begins to behave as a liquid. Such afluidized bed of solids will exert a pressure proportional to the depthof the bed and the density of gas/solids mixture in the same manner aswould a liquid of similar density and depth. Typically, such beds offluidized solids will range in depth from a few feet to as much as 30feet or more and will exhibit a measured density ranging from a fewpounds per cubic foot to over 40 pounds per cubic foot. The resultingpressure exerted by the column of fluidized solids will range from aslittle as 1 pound per square inch (psi) to as high as 10 psi or more.Moreover, the bed of solids is often quite turbulent, meaning thepressure at any one point in the bed fluctuates with time and will varyfrom point to point at a given depth in the bed. For this reason, it isimportant to design gas distributors with sufficient pressure drop so asto overcome the pressure fluctuations that are expected at the locationof the gas distributor in the bed. A typical “rule of thumb” for thedesign of gas distributors is that the minimum pressure drop should be15% of the bed pressure drop for downward pointed injection nozzles and30% of the bed pressure drop for upward pointed distributors.

In addition to maintaining a minimum pressure drop for uniformdistribution of the gas medium, injection nozzles are also designed todischarge the gas into the bed at relatively high velocity. If the gasvelocity is too low, pressure pulsations can momentarily cause solids tobe pressured backwards and flow from the bed into the injection nozzle.Such backflow of solids into an injection nozzle is undesirable as itcan lead to erosion of the injection nozzle from the continued scouringaction of the solids and/or plugging of an injection nozzle if thesolids become lodged into a solid mass. Moreover, if the solids arepressured far enough into an injection nozzle, they can then enter themain header where they are picked up by the flowing gas to be dischargedin one or more injection nozzles farther downstream. In such lattercase, the result may be severe erosion in one or more injection nozzlesdownstream from the nozzle through which the solids entered the header.To prevent backflow of solids into the injection nozzles, the velocityin the nozzles is generally maintained above a certain minimum value,typically above about 20 feet per second (fps).

A problem that continues to plague gas distributors in fluid beds iserosion of the injector nozzles at the point of discharge into the bedof solids. Over a long period of time, the impact of solid particles atthe discharge edge of the injector will cause gradual wear at theinjector tip. As the wear increases, the end of the nozzle can erode farenough back so as to destroy the point of attachment where the injectornozzle passes through the header. The result is a hole in the header anda loss of performance of the distributor. When this occurs, expensiveand time consuming repairs are required to restore the performance ofthe grid or ring.

One widely used process in the petroleum refining industry that makesuse of beds of finely divided solids is the fluid catalytic cracking(FCC) process. The FCC process is used for the cracking of heavy boilinggas oil streams to produce more valuable, lighter boiling products, suchas gasoline and lighter hydrocarbons. The FCC process uses solidcatalysts in powder form to facilitate the breaking of the carbon-carbonatomic bonds of the gas oil feed to form smaller molecules that liewithin the gasoline boiling range. In addition to the gasoline product,the process also produces substantial yields of lighter gases, such aspropane and butane, which are recovered and converted to valuableproducts. Fluid catalytic cracking is the most widely used “conversion”process in petroleum refining and several million barrels per day of FCCcapacity have been installed since the process inception in the early1940's. As such, the FCC process is of great economic value and istypically the most profitable unit in a petroleum refinery in the UnitedStates as well as in most refineries around the world.

The catalyst used in the FCC process is a finely divided solid composedof mostly silica and alumina in both crystalline and amorphous form. Theuse of a powdered catalyst has been the key feature contributing to thesuccess of the FCC process and has lead to the development of an entirearea of process operations that has come to be known as “fluidization.”The finely divided powder catalyst can be made to behave as a fluid whenit is properly aerated or “fluidized” by means of air or another gas.The fluidized powder can be made to flow in lines and will establish alevel within a vessel, as would a liquid. A fluidized power will alsogenerate a hydraulic pressure head proportional to the density and thedepth of the mixture within a vessel or in a vertical standpipe as woulda fluid. The powder can also be pneumatically transported by a gasstream when the gas has sufficient velocity. The ability to flow thepowdered catalyst between vessels has been of tremendous benefit in thedevelopment of a viable catalytic cracking process. Earlier attempts touse a fixed bed of catalyst pellets were largely handicapped by the needto regenerate the catalyst frequently to remove deposits of “coke” thatare a by-product of cracking. The coke, mostly carbon with some hydrogenand sulfur, deactivates the catalyst and must be removed by means of acombustion step. By use of a “fluidizable” catalyst, the catalyst can becontinuously circulated between the reaction and regeneration vessels ofa FCC unit so that there is no need for a cyclical process in order toaccomplish the reaction and regeneration steps.

In the FCC process large volumes of air are used in the Regeneratorvessel to remove coke from the catalyst and restore catalyst activity.The air is typically injected into a bed of coked catalyst by means ofpipe grid or ring type distributors. The FCC process also makes use oflarge pipe or ring type distributors in the stripping section where thespent catalyst is contacted with steam to remove entrained hydrocarbonsbefore the catalyst is sent to the regenerator. Smaller pipe or ringdistributors are used elsewhere in the FCC process to inject eithersteam or air to keep the powdered catalyst in a “fluidized” or aeratedstate. Injection nozzles used in each of these areas of the FCC processmay be subject to erosion, as described above.

A number of attempts have been made to improve injection nozzle designto reduce the harmful effects of erosion and extend the useful life ofthe distributor. These include the use of exotic alloys and ceramicmaterials to make the injection nozzle itself harder and more resistantto erosion, protecting the discharge end of the injection nozzle withhard surfacing such as metal overlays or refractory layers, and/orchanges in the design of the nozzle.

A current state-of-the-art air distributor design for an FCC regeneratormakes use of a pipe grid distributor and a two-stage injection nozzledesign. Such a design is shown in FIG. 1A, which is a plan view of apipe grid distributor consisting of three identical grids in atriangular arrangement to cover the circular cross-section of an FCCRegenerator. FIG. 1B is an elevation view of one of the pipe gridsshowing how the main air supply trunk enters from the bottom, with threebranches that also support the grid. All of the grids are installed atthe same elevation in the bed of powdered catalyst so as to have, asnearly as possible, a uniform pressure into which the air is discharged.FIG. 1C is a cross section of one of the grid arms showing thearrangement of the downward-directed nozzles at 45 degrees fromvertical. This pipe grid design has proven very efficient at physicallydistributing the air over the cross section of the catalyst bed so thatthe coke burning is uniform.

FIG. 1D is a cross section of one of the air injection nozzles thatutilizes a two-stage or so-called “Borda” tube. FIGS. 1E-1H containsvarious views showing the nozzle arrangement inside one of the gridarms. The metal grid arms are covered in erosion resistant refractory toprotect both the grid arms themselves and the final length of theinjection nozzles from erosion by the wearing action of the catalystparticles.

The Borda tube or two-stage nozzle consists of a straight tube with aconcentric orifice at the inlet end. In the Borda tube design, theorifice is sized so as to provide sufficient pressure drop to promoteuniform distribution of air across the grid, where the pressure drop istypically between about 1 and 3 psi. The orifice is followed by a largerdiameter tubular section that slows down the gas so that the dischargevelocity into the bed of solids does not cause excessive erosion and/orattrition of the catalyst. See, for example, Joseph W. Wilson, “FluidCatalytic Cracking,” p. 140-141, Penwell Publishing, 1997, describinguse of a Borda tube as an injection nozzle in FCC applications.

The recommended length for the Borda tube is a minimum of six times thetube diameter to allow the flow in the tube to become fully developedfollowing the nozzle orifice. It has been established in practice that,if the nozzle is too short, the flow at the discharge will be turbulentand excessive erosion will result at the nozzle tip.

Although the Borda tube design and the use of hard materials forconstruction of the nozzle and/or protection of the nozzle tip havegreatly improved the life of the grid distributors in FCC service, thesedesigns are still subject to erosive wear that requires periodicreplacement of either individual nozzles in a grid arm or replacement ofthe entire grid arm. These types of repairs are difficult to make andcan lengthen the time required to perform routine maintenance duringscheduled down periods.

Another example of an air distributor used for FCC catalyst regenerationprocess is disclosed in U.S. Pat. No. 4,223,843. As disclosed therein,the air distributor includes a plurality of nozzles in a header ring andin a cylindrical housing, with each nozzle formed with a diverging borefor ejecting high pressure air. The diverging bore of each of thenozzles is formed at a half angle of less than 7° for providing amaximum air velocity without destruction of the spent catalyst.

U.S. Pat. No. 4,460,130 discloses an injector nozzle disposed externalto the manifold having a central opening and an inlet extending from thenozzle to the central passage. The cross-sectional area of the centralopening in the nozzle in the direction of flow is smaller at least atone point than that of the inlet such that a major portion of thepressure drop in the gas flowing from the central passage through theinlet and the nozzle is created by the nozzle. The central openingoutwardly diverges at an angle of less than 15° to avoid jetting andformation of eddy currents.

There still exists a need in the art for gas distribution devices thatare subject to less erosive wear.

SUMMARY OF THE DISCLOSURE

In one aspect, embodiments disclosed herein relate to an injectionnozzle for use in a gas distribution device, the injection nozzleincluding: a tube having a fluid inlet and a fluid outlet; wherein theinlet comprises a plurality of flow restriction orifices.

In another aspect, embodiments disclosed herein relate to an injectionnozzle for use in a gas distribution device, the injection nozzleincluding: a tube having a fluid inlet and a fluid outlet; wherein thefluid inlet comprises an annular orifice surrounding a flow restrictiondevice.

In another aspect, embodiments disclosed herein relate to a gasdistribution apparatus, including: a distribution manifold in fluidcommunication with a gas source and a plurality of injection nozzles;each of the plurality of injection nozzles including a fluid inletdisposed within the distribution manifold and a fluid outlet; whereinthe fluid inlet comprises a plurality of flow restriction orifices. Insome embodiments, the above described gas distribution apparatus may bedisposed in a vessel, such as for distributing a gas in vessel forconducting polymerization reactions, spent catalyst regeneration, orcoal gasification.

In another aspect, embodiments disclosed herein relate to a gasdistribution apparatus, including: a distribution manifold in fluidcommunication with a gas source and a plurality of injection nozzles;each of the plurality of injection nozzles including a fluid inletdisposed within the distribution manifold and a fluid outlet; whereinthe inlet comprises an annular orifice surrounding a flow restrictiondevice. In some embodiments, the above described gas distributionapparatus may be disposed in a vessel, such as for distributing a gas invessel for conducting polymerization reactions, spent catalystregeneration, or coal gasification.

Other aspects and advantages will be apparent from the followingdescription and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A (plan view) and 1B (elevation view) illustrate a prior art pipegrid distributor.

FIG. 1C is a cross-sectional view of a grid arm of the prior art pipegrid distributor of FIG. 1A, including a Borda tube injection nozzle.

FIG. 1D is a detail view of a Borda tube used in FIG. 1C.

FIGS. 1E-1H several perspective views of the Borda tube arrangementwithin the grid arm of FIG. 1C.

FIGS. 2A (cross-sectional view) and FIG. 2B (inlet end view) illustrateinjection nozzles according to embodiments disclosed herein.

FIGS. 3A (cross-sectional view) and FIG. 3B (inlet end view) illustrateinjection nozzles according to embodiments disclosed herein.

FIGS. 4A (cross-sectional view) and FIG. 4B (inlet end view) illustrateinjection nozzles according to embodiments disclosed herein.

FIGS. 5A (cross-sectional view) and FIG. 5B (inlet end view) illustrateinjection nozzles according to embodiments disclosed herein.

FIGS. 6A (cross-sectional view) and FIG. 6B (inlet end view) illustrateinjection nozzles according to embodiments disclosed herein.

FIGS. 7A (cross-sectional view) and FIG. 7B (inlet end view) illustrateinjection nozzles according to embodiments disclosed herein.

FIGS. 8A (cross-sectional view) and FIG. 8B (inlet end view) illustrateinjection nozzles according to embodiments disclosed herein.

FIGS. 9A (cross-sectional view) and FIG. 9B (inlet end view) illustrateinjection nozzles according to embodiments disclosed herein.

FIGS. 10 is a cross-sectional view of a pipe distributor grid armincluding injection nozzles according to embodiments disclosed herein.

FIGS. 11 is a cross-sectional view of a pipe distributor grid armincluding injection nozzles according to embodiments disclosed herein.

FIG. 12 is a cross sectional view of a vessel including a flat platedistributor including injection nozzles according to embodimentsdisclosed herein.

FIG. 13 is a cross sectional view of a vessel including a flat platedistributor including injection nozzles according to embodimentsdisclosed herein.

FIG. 14A-14E show the internal flow pattern for a standard Borda tubeinjection nozzle as developed from computation fluid dynamics (CFD)analysis.

FIGS. 15A-15K show sequential frames from CFD animation of a standardBorda tube injection nozzle that illustrate the movement and instabilityof the jet from the orifice and how the instability is present all theway to the end of the tube.

FIGS. 16-20 show the internal flow pattern for Borda tubes and modifiedBorda tubes based on CFD analysis.

FIGS. 21-25 show the internal flow pattern for injection nozzlesaccording to embodiments disclosed herein based on CFD analysis.

FIGS. 26-31 compares the internal flow pattern for injection nozzlesaccording to embodiments disclosed herein based on CFD analysis to thatfor standard Borda tubes.

DETAILED DESCRIPTION

In one aspect, embodiments herein relate to an apparatus for theinjection of a gaseous stream into a bed of fluidized solids. Morespecifically, embodiments disclosed herein relate to an injection nozzlethat may result in a gas velocity profile so as to reduce or avoiderosion of the injection nozzle.

Injection nozzles may have a fluid inlet, in fluid communication with agas distribution manifold, and a fluid outlet, in fluid communicationwith a vessel, for example. The fluid inlet of injection nozzlesaccording to embodiments disclosed herein may include one or more fluidpathways parallel, perpendicular, or transverse to the nozzle axis. Thefluid pathways may be designed and distributed on the nozzle so as toresult in one or more of: a desired pressure drop across the nozzle; astable gas velocity profile; a uniform velocity profile that may becentered with the nozzle outlet; and a maximum velocity less than thatwhich may cause attrition of solid particles being fluidized.

Examples of injection nozzles according to embodiments disclosed hereinare illustrated in FIGS. 2-9. Although features of the injection nozzlesare illustrated in the Figures as generally circular/cylindrical, othershapes/profiles may be used, such as square, rectangular, hexagonal,octagonal, etc. As such, when referring to diameter herein, it isunderstood that the diameter is an equivalent diameter for shapes otherthan circular.

Referring now to FIGS. 2A (cross-sectional view) and 2B (inlet endview), an injection nozzle according to embodiments disclosed herein isillustrated. Injection nozzle 10 may include tube 12 having a fluidinlet end 14 and a fluid outlet 16. Fluid inlet 14 may be formed, forexample, from a plurality of radial flow restriction orifices 17distributed circumferentially through tube 12. As used herein,“plurality” refers to two or more, even if illustrated as having adifferent number. As shown in FIG. 2B, the inlet end may be capped witha back plate 18, having no flow openings, so as to only allow flow ofgas radially into tube 12 via radial flow restriction orifices 17.

The number and diameter of the radial flow restriction orifices maydepend upon the desired pressure drop through tube 10. The plurality ofradial flow restriction orifices 17 may be distributed through the tube12 in a circumferentially row. Other embodiments may include additionalcircumferential rows of radial flow restriction orifices.

A ratio of an inner diameter D_(T) of the tube outlet to a diameterD_(O) of a radial flow restriction orifice may be greater than 2:1. Inother embodiments, the ratio of an inner diameter D_(T) of the tubeoutlet to a diameter D_(O) of a radial flow restriction orifice may bewithin the range from 2:1 to 20:1.

The plurality of radial flow restriction orifices may be disposedthrough the tube a length L from an inlet axial end of the tubeproximate the inlet. In some embodiments, the length L may be less than2 times the inner diameter of fluid outlet 14; less than 1.5 times theinner diameter of fluid outlet 14 in other embodiments, less than 1times the inner diameter of fluid outlet 14 in other embodiments; andless than 0.5 times the inner diameter of fluid outlet 14 in yet otherembodiments. In other embodiments, the radial flow restriction orificesmay be positioned as close to the axial end as possible so as to provideboth manufacturability and structural integrity.

Referring now to FIGS. 3A (profile view) and 3B (inlet end view), aninjection nozzle according to embodiments disclosed herein isillustrated. Injection nozzle 20 may include tube 22 having a fluidinlet 24 and a fluid outlet 26. Fluid inlet 24 may be formed, forexample, from a plurality of axial flow restriction orifices 27distributed axially through inlet plate 28.

As shown in FIG. 3B, the axial flow orifices 26 may be distributed overinlet plate 28 using an even spacing. Use of an even spacing may allowfor ease of manufacture, structural integrity. More importantly, evenlyspaced axial flow restriction orifices may allow for development of auniform, centered flow profile.

Comparing FIG. 3A and FIG. 4A, where like numerals represent like parts,axial flow restriction orifices 26 may have a length L_(o) that may betailored to achieve a desired pressure drop or velocity profile. In someembodiments, length L_(o) may allow for flow within the axial flowrestriction orifice 27 to stabilize, thus exiting the orifice at a moreuniform velocity profile, correspondingly resulting in a more uniformvelocity profile at fluid outlet 26. For example, length L_(o) may be atleast 4 times the diameter of an axial flow restriction orifice in someembodiments; at least 5 times the diameter of an axial flow restrictionorifice in yet other embodiments.

The length from an orifice outlet end 32 to fluid outlet 24 should alsobe sufficient to develop a stable, uniform velocity profile. In someembodiments, a ratio of an axial length of the tube to an axial lengthof the plurality of flow restriction orifices may be at least 4:1;within the range from 5:1 to 50:1 in other embodiments.

The number and diameter of the axial flow restriction orifices may alsodepend upon the desired pressure drop through tube 20. In someembodiments, a ratio of an inner diameter of the tube outlet to adiameter of an axial flow restriction orifice is greater than 2:1;within the range from 2:1 to 20:1 in other embodiments.

As illustrated in FIGS. 5A (profile view) and 5B (inlet end view), wherelike numerals represent like parts, axial flow restriction orifices 26may be tapered. For example, axial flow orifices 26 may increase indiameter from an orifice inlet end 30 to an orifice outlet end 32, wherethe outer diameter may taper at an angle a up to about 15° in someembodiments; at an angle a between about 5° and 15° in otherembodiments; and at an angle a between 7.5° and 12.5° in yet otherembodiments.

Referring now to FIGS. 6A (profile view) and 6B (inlet end view), aninjection nozzle according to embodiments disclosed herein isillustrated. Injection nozzle 60 may include tube 62 having a fluidinlet 64 and a fluid outlet 66. Fluid inlet 64 may be formed, forexample, as an annular orifice 68 surrounding a flow restriction device70. As illustrated in FIG. 6A, flow restriction device 70 may include adisk 70D, appropriately suspended in the center of the inlet end of tube62.

The width W of annular orifice 68 may depend upon the desired pressuredrop through nozzle 60, among other factors. In some embodiments, adiameter of disk 70D may range from 0.5 to 0.95 times the inner diameterof tube 62; from 0.6 to 0.85 times the inner diameter of tube 62 inother embodiments.

Comparing FIG. 6A and FIG. 7A, where like numerals represent like parts,flow restriction device 70 may have a length L_(A) that may be tailoredto achieve a desired pressure drop or velocity profile. In someembodiments, length L_(A) may allow for flow within the annular orifice68 to stabilize, thus exiting the orifice at a more uniform velocityprofile, correspondingly resulting in a more uniform velocity profile atfluid outlet 66. For example, length L_(A) may be at least 4 times widthW; at least 5 times width W in yet other embodiments.

The length from an annular orifice outlet end 72 to fluid outlet 66should also be sufficient to develop a stable, uniform velocity profile.In some embodiments, a ratio of an axial length L_(T) of the tube to alength L_(A) of the annular flow orifice may be at least 4:1; within therange from 5:1 to 50:1 in other embodiments.

As illustrated in FIGS. 8A (profile view), 8B (inlet end view), 9A(profile view), and 9B (inlet end view), where like numerals representlike parts, annular flow orifice 66 may be tapered, such as through useof a flow restriction device 70C that may be conical. For example,annular flow orifice 68 may increase in diameter from an orifice inletend 72 to an orifice outlet end 74, where the outer diameter may taperat an angle β up to about 15° in some embodiments; at an angle β betweenabout 5° and 15° in other embodiments; and at an angle β between 7.5°and 12.5° in yet other embodiments. As illustrated in FIG. 9A, theoutlet end of conical flow restriction device 70C may be truncated(resulting in a frustoconical flow restriction device 70F).

Injection nozzles according to embodiments disclosed herein, asdescribed above, may provide for a stable velocity profile. Suchinjection nozzles may provide for a uniform velocity profile centered atthe nozzle outlet. Injection nozzles according to embodiments disclosedherein may avoid generation of areas having a high velocity or localizedjets that may cause particle attrition. Additionally, injection nozzlesdisclosed herein may avoid generation of areas having a negative axialvelocity proximate the nozzle outlet, thus resulting in a low nozzleerosion rate.

Injection nozzles described above may be disposed in a gas distributionapparatus. Injection nozzles according to embodiments disclosed hereinmay be used with all types of distribution apparatus where only agaseous phase is being distributed into a bed of fluidized solids. Forexample, distributors may include a flat plate distributor, a pipe gridsystem, a ring distributor, a dome-type distributor, and a mushroomdistributor, among others. Such distributors may be disposed in vesselsfor performing various reactions or mass transfer between the gas andsolids, including FCC catalyst regeneration vessels, gas-phasepolymerization vessels, coal gasification, and iron ore reduction, amongothers.

Referring now to FIGS. 10 and 11, where like numerals represent likeparts, injection nozzles according to embodiments disclosed herein,disposed in a gas distribution apparatus, are illustrated. Gasdistribution apparatus 80 may include a ring type distributor (notillustrated) having a gas distribution manifold 82 in fluidcommunication with a gas source and a plurality of injection nozzles 84.Each of the injection nozzles may include a fluid inlet 86 disposedwithin the distribution manifold and a fluid outlet 88. In someembodiments, such as shown in FIG. 10, the fluid outlet 88 may belocated proximate an outer circumference 89 of gas distribution manifold82. In other embodiments, such as shown in FIG. 11, the fluid outlet 88may terminate at a point external to gas distribution manifold 82.

Similarly, referring now to FIGS. 12 and 13, where like numeralsrepresent like parts, injection nozzles according to embodimentsdisclosed herein, disposed in a gas distribution apparatus, areillustrated. Gas distribution apparatus 90 may include a flat platedistributor 91 within a vessel 92, having a gas distribution manifold 93in fluid communication with a gas source 94 and a plurality of injectionnozzles 95. Each of the injection nozzles may include a fluid inlet 96disposed within the distribution manifold and a fluid outlet 97. In someembodiments, such as shown in FIG. 12, the fluid outlet 97 may belocated proximate a top surface 98 of flat plat 99. In otherembodiments, such as shown in FIG. 13, the fluid outlets 97 mayterminate at a point above top surface 98 of flat plate 99.

As mentioned above, injection nozzles according to embodiments disclosedherein may be used in gas distribution apparatus used for FCC catalystregeneration, for example. Injection nozzles according to embodimentsdisclosed herein may additionally be used in other portions of acracking process as well, such as illustrated in and described withrespect to FIG. 1 of U.S. Pat. No. 5,314,610, which is incorporatedherein by reference. As described in the '610 patent, gas distributionapparatus may be used for injection of a stripping medium, such as steamor nitrogen, into a catalytic cracking reaction vessel, or for injectionof oxygen or air for combustion and removal of coke from a spentcatalyst.

EXAMPLES

The following examples are derived from modeling techniques and althoughthe work was actually achieved, the inventors do not present theseexamples in the past tense to comply with applicable rules.

Simulations of injection nozzles according to embodiments disclosedherein are compared to Borda tubes and modified Borda tubes using“computational fluid dynamics” (CFD). CFD is used to examine and comparethe flow patterns resulting from a given injection nozzle configuration,as illustrated in FIGS. 14-17. As will be shown, injection nozzlesaccording to embodiments disclosed herein may reduce the potential forflow instabilities and potential for erosive wear at the nozzle tip. TheCFD studies are conducted using identical conditions for each injectionnozzle configuration simulated such that the air flows and pressuredrops were the same for each design.

Comparative Example 1

Referring to FIGS. 14A-14E, CFD results for a standard Borda typeinjection nozzle that is widely used for gas distributors in fluidizedbeds is illustrated. The nozzle is 9 inches in length, has an innerdiameter at the outlet of 1.5 inches, and the inlet orifice is 1.04inches in diameter. FIG. 14A is a cross-section of a gas distributionheader, showing the flow velocity vectors inside the header, the Bordatube, and the surrounding bed of solids. As would be expected, there isa high velocity jet as the gas accelerates through the orifice anddiverges into the larger diameter of the Borda tube downstream oforifice.

FIG. 14B shows the velocity vectors on a single plane that cuts througha cross section of the header and Borda tube and out into a bed ofsolids. The plane is oriented so as to be parallel to the direction ofthe general gas flow in the header. The CFD results indicate that thegas jet exiting the orifice is influenced by the gas flow in the header.Moreover, the animated CFD shows that the gas jet is not stable, butsways from side-to-side inside the Borda tube.

FIGS. 14C and 14D are a close up snapshot of the gas jet from theorifice viewed from two different directions, one view being in thedirection of the gas flow in the header and the second view beingperpendicular to the direction of the gas flow. It is clear from theseviews that the jet from the orifice is being influenced by the flow ofgas in the header.

FIG. 14E is a view along a single plane through the center of the Bordatube with the orientation of the plane being parallel to the directionof gas flow in the header. It is surprising to find that the instabilityof the gas jet persists beyond the end of the nozzle and into the bed offluidized solids despite the nozzle having the minimum recommendedlength to diameter ratio (LID) of 6.0. Moreover, the instability of thegas jet actually results in a negative axial velocity in one part of thetube. The animated version of the CFD study shows that the negativevelocity region is not stable, but moves from side to side in the tube,as illustrated in FIG. 15A, an end view of the nozzle inlet, and FIGS.15B-15K, which contain sequential (equal time interval) snapshots fromthe CFD analysis of a Borda tube injection nozzle showing how the jetmoves from side to side in the Borda tube. It is clear from theseresults that this nozzle design may allow solids to backflow into theregion of negative axial velocity only to be picked up and ejected athigh velocity when the gas jet reverses sides in the tube. The behaviorof the unstable gas jet coincides with observed wear pattern on thesetypes of nozzles after use for a period of time.

Comparative Examples 2-5

Referring now to FIGS. 16-20 (Comparative Examples 1-5), snapshot viewsalong an axial plane through various injection modified Borda tubeconfigurations are illustrated. All of the injection nozzles areevaluated under the same conditions of inlet pressure with the orificeopenings sized to provide a constant pressure drop of 2.1 psi across theinjector. Each nozzle is 9 inches in length and has a 1.5 inch innerdiameter (L/D of 6).

Comparative Example 1 (Repeat)

FIG. 16 is the standard Borda tube with a single orifice, as previouslyshown in FIGS. 14 and 15, shown again here for reference.

Comparative Example 2

In FIG. 17, the Borda tube includes a double orifice (each ¼-inch inlength and having a diameter of 1.04 inches) with a 0.75-inch spacebetween the orifices. The CFD results indicate no improvement in thestability of the jet or the presence of regions of negative axialvelocity in the nozzle tube as compared to a standard Borda tube.

Comparative Example 3

In FIG. 18, the orifice includes a short sloped section on thedownstream end. Again, the CFD results indicate no improvement in thestability of the jet or the presence of regions of negative axialvelocity in the nozzle tube.

Comparative Example 4

In FIGS. 19A (profile view) and 19B (end view of nozzle inlet), thethickness of the orifice is increased from ¼-inch to 1-inch in length.This arrangement demonstrates less instability in the CFD results.However, the region of negative axial velocity is still present althoughthe location of the negative velocity region is more stable.

Comparative Example 5

In FIGS. 20A (profile view) and 20B (end view of nozzle inlet), thethick nozzle includes a long sloped region at the outlet end of theorifice. This arrangement demonstrates a very stable velocity profile.However, the gas jet is not centered in the tube and there is arelatively large, though stable, area of negative axial velocity.

The CFD analyses of a Borda tube and modified Borda tubes in FIGS. 16-20exhibit unstable flow and/or negative axial velocity, each of which isan undesired flow characteristic of a gas injection nozzle.

Examples 1-5

Referring now to FIGS. 21-25 (Examples 1-5), snapshot views along anaxial plane through injection nozzles according to embodiments disclosedherein are illustrated. All of the injection nozzles are evaluated underthe same conditions as Comparative Examples 1-5 (same inlet pressurewith the orifice openings sized to provide a constant pressure drop of2.1 psi across the injector). Each nozzle is 9 inches in length and hasa 1.5 inch inner diameter (LID of 6).

Example 1

FIGS. 21A (profile view) and 21B (end view of nozzle inlet) illustrate aCFD analysis of an orifice similar to that illustrated in theembodiments described with relation to FIGS. 6A and 6B. The orificeconfiguration includes an annular opening surrounding a flat disk (0.75inches in diameter and ¼-inch in length suspended in the center at theinlet of the injection nozzle. This nozzle has a very stable velocityprofile. However, the velocity profile is not centered at the outlet.Additionally, there may be localized regions where backflow might occurand the nozzle may be difficult to manufacture.

Example 2

FIGS. 22A (profile view) and 22B (end view of nozzle inlet) illustrate aCFD analysis of an orifice similar to that illustrated in the embodimentdescribed with relation to FIGS. 9A and 9B. The orifice configurationincludes a tapered cone suspended at the inlet of the nozzle to form theannular orifice opening. This nozzle performs as well as that of FIGS.21A and 21B from a stability standpoint, but shows improvement in thatthe velocity profile is almost perfectly centered in the nozzle tube.However, the nozzle may be difficult to manufacture.

Example 3

FIGS. 23A (profile view) and 23B (end view of nozzle inlet) illustrate aCFD analysis of an orifice similar to that illustrated in the embodimentdescribed with relation to FIGS. 3A and 3B. The orifice configurationincludes seven (7) smaller orifices to provide the same pressure drop asthe single orifice arrangement. This arrangement exhibits a fairlystable velocity profile, and, the velocity profile at the nozzle exit isvery uniform. There are some areas of negative axial velocity, but theseare confined to the inlet half of the nozzle and do not reach the nozzletip.

Example 4

FIGS. 24A (profile view) and 24B (end view of nozzle inlet) illustrate aCFD analysis of an orifice similar to that illustrated in the embodimentdescribed with relation to FIGS. 4A and 4B. The orifice configurationincludes a multi-orifice (7 hole) arrangement similar to Example 3,except that the thin orifice plate (¼-inch) has been replaced with athick (1-inch) plate. The inclusion of the thick orifice plate improvesthe stability of the velocity profile compared to Example 3, while alsoshowing a very uniform velocity profile at the injection nozzle outlet.Moreover, the point at which the velocity profile becomes uniform occurssooner than with the thin orifice arrangement of Example 3.

Example 5

FIGS. 25A (profile view) and 25B (end view of nozzle inlet) illustrate aCFD analysis of an orifice similar to that illustrated in the embodimentdescribed with relation to FIGS. 2A and 2B. The orifice configurationincludes a multi-orifice arrangement with eight (8) holes that have beenmoved to the side of the tube rather than being placed on the backplate. There are no openings on the back plate. Again, the orifice areais sized to provide the same overall nozzle pressure drop of 2.1 psi asmaintained for all previous arrangements. The CFD studies show that thisarrangement results in a stable, uniform velocity profile. In theanimated CFD result, there is almost no movement detected in thevelocity profile. Moreover, the nozzle design is easy to manufacturerelative to the standard Borda tube of Comparative Example 1.

Example 6

FIGS. 26-31 compare CFD analyses of orifice similar to that illustratedin FIGS. 2A and 2B with a CFD analysis of the standard Borda tube ofComparative Example 1 (illustrated in FIG. 16 and repeated as FIGS. 27,29, and 31 for convenience, where 27A, 29A, and 31A represent a profileview, and 27B, 29B, and 31B represent an end view of the nozzle inlet).The orifice configurations include multi-orifice arrangements with eight(8) holes (FIGS. 26A (end view) and 26B (profile view of nozzle inlet),six (6) holes (FIGS. 28A (end view) and 28B (profile view of nozzleinlet), and four (4) holes (FIGS. 30A (end view) and 30B (profile viewof nozzle inlet) that have been moved to the side of the tube ratherthan being placed on the back plate. There are no openings on the backplate. Again, the orifice area is sized to provide the same overallnozzle pressure drop of 2.1 psi as maintained for all previousarrangements. The CFD studies show that these arrangements result instable, uniform velocity profiles (reduced oscillation over time)compared to the standard Borda Tube. The CFD studies also show thatmoving from eight (8) to six (6) to four (4) openings improveduniformity in the outlet velocity.

As described above, injection nozzles according to embodiments disclosedherein may advantageously provide for one or more of a stable velocityprofile, a uniform velocity at the injection nozzle outlet, and limitedregions having a negative flow velocity. Advantageously, such injectionnozzles may result in one or more of decreased erosion, decreasedcatalyst attrition, and improved gas distribution.

While the disclosure includes a limited number of embodiments, thoseskilled in the art, having benefit of this disclosure, will appreciatethat other embodiments may be devised which do not depart from the scopeof the present disclosure. Accordingly, the scope should be limited onlyby the attached claims.

1-37. (canceled)
 38. A process of cracking a hydrocarbon feedstock, suchas a fluid catalytic cracking (FCC) process, the process comprising:contacting hot regenerated catalyst particles from a catalystregenerator with a hydrocarbon feed in a riser reactor to form aneffluent comprising a cracked hydrocarbon product and a spent catalyst;separating the spent catalyst from the cracked hydrocarbon product in aseparation vessel via a stripping medium fed through a first gasdistribution apparatus to recover an overheads hydrocarbon fraction anda spent catalyst fraction; regenerating the spent catalyst fraction in aregeneration vessel via contact with a regeneration gas fed through asecond gas distribution apparatus to recover the hot regeneratedcatalyst particles; wherein at least one of the first gas distributionapparatus and the second gas distribution apparatus comprises: adistribution manifold in fluid communication with a gas source and aplurality of injection nozzles; each of the plurality of injectionnozzles comprising a fluid inlet disposed within the distributionmanifold and a fluid outlet; and wherein the fluid inlet comprises aplurality of flow restriction orifices.
 39. The process of claim 38,wherein the fluid outlet is proximate an outer circumference of thedistribution manifold.
 40. The process of claim 38, wherein the tubeoutlet is external to an outer circumference of the distributionmanifold.
 41. The process of claim 38, wherein the plurality of flowrestriction orifices comprises a plurality of radial flow restrictionorifices distributed circumferentially through the tube.
 42. The processof claim 41, wherein an axial end of the tube proximate the plurality ofradial flow restrictions orifices is capped.
 43. The process of claim41, wherein a ratio of an inner diameter of the tube outlet to andiameter of a radial flow restriction orifice is greater than 2:1. 44.The process of claim 41, wherein the plurality of radial flowrestriction orifices are disposed through the tube a length L from anaxial end of the tube proximate the inlet, wherein the length L is lessthan 2 tube inner diameters.
 45. The process of claim 38, wherein theplurality of flow restriction orifices are axially aligned with thetube.
 46. The process of claim 45, wherein a ratio of an axial length ofthe tube to an axial length of the plurality of flow restrictionorifices is at least 4:1.
 47. The process of claim 45, wherein a ratioof an inner diameter of the tube outlet to an diameter of a flowrestriction orifice is greater than 2:1.
 48. The process of claim 38,wherein a length of the tube is at least 5 times an inner diameter ofthe tube outlet.
 49. A process of cracking a hydrocarbon feedstock, suchas a fluid catalytic cracking (FCC) process, the process comprising:contacting hot regenerated catalyst particles from a catalystregenerator with a hydrocarbon feed in a riser reactor to form aneffluent comprising a cracked hydrocarbon product and a spent catalyst;separating the spent catalyst from the cracked hydrocarbon product in aseparation vessel via a stripping medium fed through a first gasdistribution apparatus to recover an overheads hydrocarbon fraction anda spent catalyst fraction; regenerating the spent catalyst fraction in aregeneration vessel via contact with a regeneration gas fed through asecond gas distribution apparatus to recover the hot regeneratedcatalyst particles; wherein at least one of the first gas distributionapparatus and the second gas distribution apparatus comprises: adistribution manifold in fluid communication with a gas source and aplurality of injection nozzles; each of the plurality of injectionnozzles comprising a fluid inlet disposed within the distributionmanifold and a fluid outlet; wherein the inlet comprises an annularorifice surrounding a flow restriction device.
 50. The process of claim49, wherein the fluid outlet is proximate an outer circumference of thedistribution manifold.
 51. The process of claim 49, wherein the tubeoutlet is external to an outer circumference of the distributionmanifold (tube outlet terminates at a radial distance greater than thatof the manifold).
 52. The process of claim 49, wherein the flowrestriction device comprises a disk suspended in the center of theinlet.
 53. The process of claim 49, wherein the flow restriction devicecomprises a disk suspended in the center of the inlet.
 54. The processof claim 49, wherein the flow restriction device is conical orfrustoconical.
 55. The process of claim 49, wherein a width of theannular orifice is between 0.05 and 0.25 times an inner diameter of thetube.
 56. The process of claim 49, wherein a length of the flowrestriction device is between 0.1 and 0.9 times a length of the tube.